build(env): extract Redis URL into env file

This could allow one to connect to a remote Redis instance with a powerful GPU, allowing one to offload the NLP work.

example.env

@@ -18,5 +18,10 @@ HF_HOME=/models/huggingface
 TRANSFORMERS_CACHE=/models/huggingface
 TORCH_HOME=/models/torch
 
-# Frontend
+# URLs
 FRONTEND_URL=http://localhost:5173
+BACKEND_URL=http://backend:5000
+REDIS_URL=redis://redis:6379/0
+
+# API & Scraping
+MAX_FETCH_LIMIT=1000